Myelin sheath is a layer of lipid cell membrane that covers sheath nerve fiber axon outside and consists of myelin sheath cells, which main physiological function is to act “insulation” and protection functions on nerve axon, and facilitates rapid transmission of nervous impulse. Demyelinating disease is a group of disorders featured with myelinoclasis of nerve fiber as main pathological change, which can either implicate central nervous system, or peripheral nervous system. This disease has main pathological features of: (1) nerve fiber myelinoclasis, presented in multiple small disseminated foci, or a relatively large focus formed by one or more foci in fusion; (2) demyelination lesions are distributed in alba, spinal cord or peripheral nerves, infiltrating in coatsleeve like form along inflammatory cells around veinlet.
This kind of diseases include multiple sclerosis, optical neuromyelitis, acute disseminated encephalomyelitis, diffuse sclerosis, concentric circle sclerosis, leukodystrophy, central pontine myelinolysis, acute inflammatory demyelinating polyneuropathy, chronic inflammatory demyelinating polyneuropathy; and demyelinating diseases caused by other factors, including but not limited to leukoencephalopathy caused by ischemia-anoxia diseases, subacute combined degeneration caused by nutrition deficiency diseases, subacute sclerosing panencephalitis or progressive multifocal leukoencephalopathy caused by viral infection, diabetic neuropathy (this disease is mainly presented demyelination lesion), nervous lesions of systemic lupus erythematosus (this disease is mainly presented in demyelination lesion). The research of an effective drug for alleviating myelination and promoting myelin sheath plerosis may provide an important means for preventing demyelination diseases in central and peripheral nervous systems caused by various factors.
Iridoids are a group of specific monoterpene compounds, which mother nuclei are all in ring form, having ethylenic linkage and ether linkage, and which basic skeletons are of the following structure formula.

In the molecules of iridoids, C1—OH is very active, easy to bind to a saccharide, and most of natural iridoids are glycosides, especially D-glucosides. They include but are not limited to:
(1) Common iridoid glycosides: 1) C-8 iridoid glycosides; 2) C-9 iridoid glycosides (the 9th C links to C-4); 3) C-9 iridoid glycosides (the 9th C links to C-8); 4) C-10 iridoid glycosides. The examples are morroniside, loganin, 6′-acetylasperuloside, geniposide, catalpol, allamdin, allamandin, asperuloside, aucubin, catalpin, deoxyloganin, genipin, plumericin, verbenalin, kingiside.
(2) Diffractive ring iridoid glycosides: such as gentiopicrin, amarogentin, secologanin, swertiamarin.
(3) Valeriana type iridoids, such as 7,10,2′-3 acetylpatrinoside, and 10-acetylpatrinoside.
(4) Plumeria type iridoids: such as poncirin A.
(5) Iridoids with oxo bridge between 3- and 10-positions, such as iridoid glycosides with oxo bridge between 3- and 10-positions, crescent glycoside B.
(6) Iridoids related to nepetalactone type, such as ipuranol.
(7) Transformative iridoids, such as crescent glycosides A and B, poncirin B with ternary oxaspiro structure at 8-position.
(8) Formed with several iridoids directly via ester bond or via linkage of terpenes, phenols. Examples are acevaltratum, deacetylasperuloside acid methyl ester.
The inventors of the present invention conduct wide and deep researches on iridoid compounds such as morroniside and loganin, and find the iridoid compounds have function of alleviating myelinoclasis and inflammatory cell infiltration in nervous system, and promoting myelination and plerosis, and thus the present invention is carried out.